Piston Rings - Pistons - Piston Pins; Connecting Rods - Kohler KD 425-2 Workshop Manual

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CHECKS AND OVERHAUL
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21
22
23
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Piston rings - Pistons - Piston pins

Check the wear of piston rings by fitting them into the cylinder throu-
gh the lower end and measuring the end gap (fig.20). The values
should be:
Piston ring Fitting mm
Compression
0,30
Oil scrapper 0,25
Check that the rings move freely in the grooves and check the ring/
groove clearance using a feeler gauge (fig.21).
If the clearance exceeds the values shown in the table, renew the pi-
ston and the piston rings.
Piston ring
1st Compression
2nd Compression
3rd Oil scrapper
Piston rings must always be renewed after dismantling the
piston.
Piston diameter check: The diameter of the piston must be measured
at approximately 18 mm from the base (fig.22).
Engine
KD 425-2
Check the clearance between cylinder and piston, if it is greater than
0.120 mm both cylinder and piston must be replaced. Assembly clea-
rance between piston pin and piston in millimetres:
Fitting mm
0,003 ÷ 0,013

Connecting rods

The connection between the connecting rod small end and the wri-
st pin is without a bushing. Assembly clearance between connecting
rod small end and piston pin in millimetres:
Engine
Ø Piston pin
KD 425-2
21,997
Checking parallelism between the two axes of the connecting rod
(fig.23):
1. Fit the wrist pin in the hole in the small end of the connecting rod
and fit a calibrated pin into the big end (with bush fitted).
KD 425-2 Workshop Manual_cod. ED0053029360_1° ed_ rev. 00
Max. wear mm
÷ 0,50 0,80
÷ 0,50 0,80
Max. wear mm
A = 0,22
B = 0,18
C = 0,16
Diameter mm
84,910 ÷ 84,940
Max. wear mm
0,050
Assy.
clearance
mm
mm
÷ 22,002 0,023 ÷ 0,038
Max wear
mm
0,070